Linking vegetation cover patterns to hydrological responses using two process-based pattern indices at the plot scale

Abstract

Vegetation cover pattern is one of the factors controlling hydrological processes. Spatially distributed models are the primary tools previously applied to document the effect of vegetation cover patterns on runoff and soil erosion. Models provide precise estimations of runoff and sediment yields for a given vegetation cover pattern. However, difficulties in parameterization and the problematic explanation of the causes of runoff and sedimentation rates variation weaken prediction capability of these models. Landscape pattern analysis employing pattern indices based on runoff and soil erosion mechanism provides new tools for finding a solution. In this study, the vegetation cover pattern was linked with runoff and soil erosion by two previously developed pattern indices, which were modified in this study, the Directional Leakiness Index (DLI) and Flowlength. Although they use different formats, both indices involve connectivity of sources areas (interpatch bare areas). The indices were revised by bringing in the functional heterogeneity of the plant cover types and the landscape position. Using both artificial and field verified vegetation cover maps, observed runoff and sediment production on experiment plots, we tested the indices' efficiency and compared the indices with their antecedents. The results illustrate that the modified indices are more effective in indicating runoff at the plot/hillslope scale than their antecedents. However, sediment export levels are not provided by the modified indices. This can be attributed to multi-factor interaction on the hydrological process, the feedback mechanism between the hydrological function of cover patterns and threshold phenomena in hydrological processes.

Improving Soil and Water Conservation of Riparian Vegetation Based on Landscape Leakiness and Optimal Vegetation Pattern

“…Vegetation is parallel to the river course Reducing riverbank scouring and soil erosion [41] Method 3 Vegetation is distributed at the river outlet Decreasing the risk of sediment entering the river to pollute water [32] 3. Results…”

“…Vegetation is parallel to the contour line Intercepting runoff and sediment flowing from upland to lowland [9] Method 2 Vegetation is parallel to the river course Reducing riverbank scouring and soil erosion [41] Method 3 Vegetation is distributed at the river outlet Decreasing the risk of sediment entering the river to pollute water [32] 3. Results…”

“…The power number k denotes the slope of the decay curve of LI against the proportion of vegetation coverage. Here, k = 5 provides a good fit for LI to the decay curve according to the practical conditions for soil and vegetation in China [22,32]. L cal represents the calculated value of the potential leakiness of a landscape and is determined by the multiple flow direction algorithm:…”

“…Patch orientation and aggregation degree had lower LI values than the other changes, indicating that these two patterns can mitigate soil erosion with better performance. Considering the importance of compact aggregation near the outlet for intercepting runoff and sediment flowing into the river [32], the horizontal distribution and compact aggregation should be identified as optimal vegetation patterns to improve soil and water conservation. Figure 6 shows the LI values according to the classification shown in Figure 4.…”

“…In addition to the international research on LI, some efforts have been made to address the use of LI in China. To explore the application of DLI, the antecedent of LI, Liu et al [32] revised the DLI to link the vegetation cover patterns to hydrological responses in the Loess Plateau, Northwest China. In the same year, Liu et al [22] assessed the impact of erosion on the water environment with LI in Central China.…”